Analysis of histologic patterns of dermatitis in cattle in the diagnostic process.

The histologic diagnosis of some cases of bovine dermatitis can be challenging. We investigated the predominant histologic patterns of dermatitis in cattle, to propose histologic pattern analysis as a diagnostic approach. Sixty-two cases of bovine dermatitis with confirmed etiologic diagnoses were selected in a 20-year retrospective study. The cases included 13 different primary and secondary diseases, ranging from infectious (48/62, 77%) to toxic/irritant-associated diseases (14/62, 23%). The cutaneous lesions were histologically classified into 11 dermatitis patterns, adapted from those described for small animals. Nodular to diffuse dermatitis (22/62, 34%), perivascular dermatitis (14/62, 23%), necrotizing dermatitis (11/62, 18%), and intraepidermal pustular dermatitis (10/62, 16%) were the most common patterns, followed by panniculitis (3/62, 5%); vasculitis (1/62, 2%); and perifolliculitis, folliculitis, or furunculosis (1/62, 2%). The nodular to diffuse, perivascular, necrotizing, and intraepidermal pustular dermatitis patterns included diseases with different etiologies, while the remaining patterns covered a smaller number of distinct cutaneous diseases in each classification. Our results highlighted the histologic analysis as an efficient tool for directing diagnoses, representing a starting point for the application of this technique in large animal dermatology.